Abstract

Expressions for the electric field and impedance of a planar capacitor containing a warm inhomogeneous magnetized plasma are derived using the electrostatic approximation. The frequency of the excitation field is near and below the second electron cyclotron harmonic while the static magnetic field is parallel to the capacitor plates. The theory, which includes wave coupling and plasma nonuniformity as well as the effects of the ambipolar electric field and the anisotropy of the unperturbed distribution function, shows that the impedance exhibits a resonant structure due to longitudinal waves confined between the two hybrid resonance points. Measurements are taken during the afterglow of a pulsed, low‐pressure, argon plasma confined between planar glass walls. These measurements are found to be in good agreement with the theoretical model.